package com.nest.WorkNest.tools;

import java.util.HashMap;

/**
 * Created by only1 on 2015/8/23 0023.
 */
public class MyHashMap extends HashMap

{

    @Override

    public Object put(Object key, Object value)

    {

        //如果已经存在key，不覆盖原有key对应的value

        if (!this.containsKey(key))
            return super.put(key, value);

        return null;

    }

}
